1. Field of the Invention
The present invention relates to a dye sensitized solar cell module and a method of manufacturing the dye sensitized solar cell module, and more particularly to a dye sensitized solar cell module which has a high cell numerical aperture and a high photoelectric converting efficiency, and at the same time, has a structure improved to fabricate a plurality of cells on a single substrate in a batch without requiring a complicated step, and a method of manufacturing the dye sensitized solar cell module.
2. Description of the Related Art
A dye sensitized solar cell is proposed such as represented by Gretzel's patent, Japanese Patent No. 2664194 and Japanese Patent No. 2101079. As compared with a silicon solar cell, material is more inexpensive and does not require large-scaled manufacturing equipment. Therefore, such a dye sensitized solar cell is advantageous for a small-scaled power supply source at a low cost.
Practically to say, however, its output voltage is relatively low because a photoelectric converting efficiency of dye sensitized solar cell is far below the level of a silicon solar cell. For this reason, it is indispensable to connect a plurality of cells in series and obtain a module for the fit of a practical use.
The greatest advantage of the dye sensitized solar cell is a low cost. In this regard, in order to obtain the module, therefore, a simple method and structure at a low cost has been simultaneously demanded.
FIGS. 1A, 1B and 2 show a typical structure of a conventional dye sensitized solar cell module.
The structure shown in FIGS. 1A and 1B have been disclosed in JP-A 2001-185743 Publication (Paragraph 0081) and JP-A 2003-86822 Publication, and individual finished dye sensitized solar cells 10 shown in FIG. 1A are connected in series through a connecting lead to obtain a module 100 as shown in FIG. 1B.
The dye sensitized solar cell 10 in FIG. 1A is constituted by laminating, from a light receiving side of an incident light L (an upper part in the drawing), in order of a transparent substrate 12, a transparent conductive film 14, a dye carrying oxide semiconductor layer 16, an electrolyte layer 18, aback conductive film 20 (transparent or opaque) and a back substrate 22 (transparent or opaque). In general, a catalyst layer 24 such as Pt or C is provided on the back conductive film 20, but this is not indispensable. The cell 10 is surrounded with a sealing material 26 in fluid tightness in order to prevent a leakage of the electrolyte 18. The transparent conductive film 14, feeding an electron (e−) that is generated from the dye carrying oxide semiconductor layer 16 to an outside, is functioning as a negative electrode of the cell 10. On the other hand, the back conductive film 20, extracting the electron (e−) from the outside, is functioning as a positive electrode of the cell 10.
FIG. 1B shows the module 100 in which three dye sensitized solar cells 10 in FIG. 1A are arranged on a plane and connected in series. The positive electrode 20 and the negative electrode 14 in the adjacent cells 10 are electrically connected to each other through an electrode connecting wire 28 and are interposed between a transparent support substrate 30 and a back support substrate 32 (transparent or opaque), and are sealed with a transparent insulating filler 34 to obtain the module 100. An output terminal of the module 100 includes a positive electrode 36 and a negative electrode 38.
In order to fabricate the module 100 in FIGS. 1A and 1B, thus, it is necessary to employ a complicated step of assembling a plurality of unit cells 10 as described above.
JP-A 2002-93475 Publication has proposed a method of fabricating a module constituted by a plurality of cells in a batch as shown in FIG. 2 without depending on the assembly of the unit cell.
A dye sensitized solar cell module 200 shown in FIG. 2 is fabricated in a batch as an integral structure in which a plurality of dye sensitized solar cells 210 and a plurality of intercell regions 215 are alternately arranged on a plane. The cell 210 has the same basic structure as that of the unit cell 10 in FIG. 1A and is constituted by laminating, from a light receiving side of an incident light L (an upper part in the drawing), in order of a transparent substrate 212, a transparent conductive film 214, a dye carrying oxide semiconductor layer 216, an electrolyte layer 218, a back conductive film 220 (transparent or opaque), and a back substrate 222 (transparent or opaque). Also in this example, a catalyst layer 224 such as Pt or C is provided on the back conductive film 220, which is, however, also not indispensable.
As shown in the drawing, the transparent substrate 212 or the back substrate 222 is each made from continuous single substrate which is common to all of the cells 210. The transparent conductive film 214 and the back conductive film 220 are constituted by electrode portions 214E and 220E provided in the cell 210 and extended portions 214T and 220T reaching an inner part of the intercell region 215 from the ends of the electrode portions, respectively.
The transparent conductive film 214, feeding an electrode (e−) generated in the dye carrying oxide semiconductor layer 216 to an outside, is functioning as a negative electrode of the cell 210. On the other hand, the back conductive film 220 for extracting the electron (e−) from the outside is functioning as a positive electrode of the cell 210.
In order to connect the cells 210 in series, the extended portion 214T of the negative electrode 214 of the cell 210 on a left side and the extended portion 220T of the positive electrode 220 of the cell 210 on a right side are electrically connected by an electrode connecting portion 228, which is individually provided in the intercell region 215. A height of the electrode connecting portion 228 defines a thickness of the electrolyte layer 218. A pair of intercell insulating barriers (or barrier walls) 226 are adhered to both sides of the electrode connecting portion 228 to carry out sealing in fluid tightness. Consequently, the electrolyte 218 is sealed in the cell 210 and a region of each cell 210 is defined.
Thus, it is possible to obtain a module by fabricating a plurality of cells on a single substrate in a serial connecting form in a batch. However, it is necessary to seal both sides of the electrode connecting portion 228 with the intercell insulating barrier 226 in fluid tightness. For this reason, the electrode connecting portion 228 shall be formed in a gap surrounded by the intercell insulating barriers 226 at both sides, by which a complicated fabricating step is required.
As already mentioned above, the dye sensitized solar cell has the greatest advantage in that a manufacturing cost can be reduced in addition to its low material cost. However, there is a problem in that the manufacturing costs of both the module structures shown in FIGS. 1A, 1B and 2 are increased due to an increase in the number of module fabricating steps and the complicated fabrication steps.
Furthermore, as for a structure in which a plurality of cells is fabricated on a single substrate in a batch in a serial connecting form, some other structures have been proposed such that an electrode connecting portion is formed by a conductive material penetrating obliquely through an intercell insulating barrier as is disclosed in JP-A 2005-174679 publication, or a structure in which both cells are connected in series with a wire interposed between electrode extended portions of adjacent cells to insulate both sides of the wire with a glass frit as is disclosed in JP-A 2001-185244 publication. However, a method of forming an insulating barrier and an electrode connecting portion between adjacent cells does not show any concrete embodiment and might not be practical in use.
As another structure in which a plurality of cells is fabricated on a single substrate in a serial connecting form in a batch, furthermore, there can be proposed a structure in which polarities of the adjacent cells are alternately reversed and arranged as shown in FIG. 3.
A dye sensitized solar cell module 300 shown in FIG. 3 is fabricated in a batch as an integral structure in which regions of a plurality of dye sensitized solar cells 310 and a plurality of intercell regions 315 are alternately reversed on a plane. The cell 310 is constituted by laminating a first transparent substrate 312, a first transparent conductive film 314, a dye carrying oxide semiconductor layer 316, an electrolyte layer 318, a catalyst layer 324, a second transparent conductive film 320, and a second transparent substrate 322.
As shown in the drawing, the first transparent substrate 312 and the second transparent substrate 322 are continuous single substrates which are common to all of the cells 310, respectively. The first transparent conductive film 314 and the second transparent conductive film 320 are constituted by electrode portions 314E and 320E provided in the cell 310 and extended portions 314T and 320T reaching an inner part of the intercell region 315 from ends of the electrode portions 314E and 320E, respectively.
In the dye sensitized solar cell module 300, polarities of adjacent cells, for example, a cell 310A and a cell 310B in the drawing are reversed as described above. More specifically, in the cell 310A, the first transparent conductive film 314, feeding an electron (e−) generated in the dye carrying oxide semiconductor layer 316 to an outside, is functioning as a negative electrode, and, at the same time, said first transparent conductive film 314 is extended to the adjacent cell 310B to be functioning as a positive electrode for extracting the electron (e−) from the outside. With the structure 300, accordingly, a separate electrode connecting portion is not required.
An insulating barrier (or barrier wall) 326 seals each cell 310 in fluid tightness. Consequently, the electrolyte 318 is sealed in the cell 310 so that a region of the individual cell 310 is defined.
Thus, it is possible to obtain a module by fabricating a plurality of cells on a single substrate in a serial connecting form in a batch. However, in every other alternate cell 310, the light to be absorbed by the dye carrying oxide semiconductor layer 316 must pass through the counter electrode 324 and the electrolyte 318. Therefore, in such an arranged cell, it is impossible to avoid a reduction in a photoelectric converting efficiency. More specifically, in the case in which the light is received at an upper surface of the dye sensitized solar cell module 300, the dye carrying oxide semiconductor layer 316 of the cell 310A absorbs a light transmitted through the first transparent substrate 312 and the first transparent conductive film 314. On the other hand, the dye carrying oxide semiconductor layer 316 of the adjacent cell 310B absorbs the light that is further transmitted through the electrolyte 318 and the catalyst layer 324 such as Pt or C. In the case in which the light is received at a lower surface of the dye sensitized solar cell module 300, the cell 310A and the cell 310B are simply reversed so that the same situation can be obtained. Thus, photoelectric converting efficiencies of the alternate cells 310, that is, half cells 310 are reduced. Therefore, it is impossible to avoid the reduction in the photoelectric converting efficiency as the whole dye sensitized solar cell module 300.